Method and apparatus for storage, transport, and use of cryogenic gases in solid form

ABSTRACT

An integrated, cryogenic storage, transport, and using system for a single solid cryogenic medium comprises: a gas-tight container; a plurality of closely-packed, adjoining compartments contained therein; layered material forming walls separating and enclosing the compartments; conduit for supplying the cryogenic medium in the liquid state to the compartments; and conduit for supplying a refrigerating fluid in heat exchange relationship with the cryogenic medium so as to solidify the fluid cryogenic medium into disconnected cryogenic solid blocks of essentially uniform composition in all the compartments. The separating walls allow any two adjoining compartments to mechanically (i.e., through stresses and strains) interact directly and, if needed, at reduced rates. In the later case, the layered material is sufficiently thick and deformable relative to the compartment size to allow for the expansion of the melting solid cryogenic medium without damaging and fracturing the container. Unique features of compartment connecting, fluid feeding, fluid supply self-regulating, stress and strain relieving, and compartment wall designing are also presented, together with novel methods of using the cryogenic system.

United States Patent 1 1 3,864,927"- Feb. 11, 19-75 METHOD AND APPARATUS FOR STORAGE, TRANSPORT, AND USE OF CRYOGENIC GASES 1N SOLID FORM [76] Inventor: Chou H. Li, 379 Elm Dr., Roslyn,

[22] Filed: Dec. 14, 1972 [21] Appl. No.: 315,184

[52] US. Cl 62/47, 62/240, 114/74 A,

[51] Int. Cl. ..Fl7c 3/02 [58] Field of Search 62/47, 55, 240, 45, 54;

220/9 LG, 88 B; 114/74 A [56] References Cited UNITED STATES PATENTS 1,680,873 8/1928 Lucas-Girardville .I 62/47 2,269,174 1/1942 Birdsall 62/47 2,938,359 5/1960 Cobb, Jr, et a1. 62/47 3,147,593 9/1964 Garrett 62/7 X 3,378,351 4/1968 Ruehrwein et 62/47 X 3,545,226 12/1970 Newell 62/47X Primary ExaminerMeye r Perlin Assistant ExaminerRonald C. Capossela 57 ABSTRACT change relationship with the cryogenic medium so as to solidify the fluid cryogenic medium into disconnected cryogenic solid blocks of essentially uniform composition in all the compartments. The separating walls allow any two adjoining compartments to mechanically (i.e., through stresses and strains) interact directly and, if needed, at reduced rates. In the later case, the layered material is sufficiently thick and deformable relative to the compartment size to allow for the expansion of the melting solid cryogenic medium without damaging and fracturing thecontainer. Unique features of compartment connecting, fluid feeding, fluidi supply self-regulating, stressand strain relieving, and compartment wall designing are also presented, together with novel methods of using the cryogenic system,

36 Claims, 8 Drawing Figures 1 METHOD AND APPARATUS FOR STORAGE, TRANSPORT, AND USE OF CRYOGENIC GASES IN SOLID FORM BACKGROUND OF THE INVENTION This invention relates to improvements in a cryogenic system, and more particularly to an integrated, cryogenic storage, transport, and using system for solid cryogenic materials.

While the invention has many applications with respect to various cryogenic media, hereinafter defined as those media which normally (at atmospheric temperature and pressure) are gases but which can be liquefied and solidified at subatmospheric temperatures into liquid and solid neon, ammonia, hydrogen, oxygen, nitrogen, air, fluorine, chlorine, surfur dioxide, methane, propane, petroleum gas, ethylene, and the like. For the purpose of illustration, the description is herein restricted mostly to solid methane transported in occean-going vessels.

Natural gases, and also waste gases from petroleum distillation, contain mostly methane (CH These highenergy, low-polluting gases have high anti-knocking properties and are suitable even for high-compression, internal combustion engines. Transported in the liquefled forms in tankers, railroad cars, airplanes, or occean-going vessels, they provide instant and portable power sources and have, therefore, revolutionized the fuel and power industry. Further, CH gas lique'fication achieves a reduction in volume of over 600 times, with a corresponding reduction in shipping costs.

But the storage and.transport of CH, or other fuels in liquid form still is always'attended by fire and explosion harzards, not only to the transport vehicle itself and persons or objects contained therein, but-also to other nearby objects, vehicles, or persons. The October 1944 Cleveland, Ohio disaster from the cracking of a liquefied natural gas (LNG) storage tank, e.g.,- resulted in damage to 29 acres and 81 homes plus a loss of 130 lives. I I

It has therefore been proposed to transport methane in solid-state form, particularly in occean-going vessels.

The solid CH is to be melted for delivery upon arrival to port. Numerous advantages have been cited including still less volume than liquid per pound; minimized damage, spill, and pollution; no fire or explosion in case of ship collision or grounding; reduced risks to crew, cargo, vessel, and surrounding property or environment; and elimination of vapor condensation, liquid sloshing, and thermal stratification.

Yet the cost of solidifying the liquid CH for transport and remelting it upon arrival to port or during transfer and use is often very high. One pound of gaseous CH at an ambient temperature of 70F requires an energy expenditure of about 550 BTU to liquefy, and an additional 65 BTU to solidify. Even if the capital investments on equipment and machineries are disregarded, the expenses and times of refrigerating to freeze liquid CH and later heating to remelt it usually exceeds most, if not all, of the direct financial benefits gained in transporting CH in solid form rather than liquid.

Further, when the CH is frozen into a large mass of solid, venting is often difficult if not impossible. In addition, when such a large mass is thawed or melted, simultaneously across a large dimension such as the top surface, the volume expansion due to heating or melting introduces severe stresses and strains on the container walls. This is because one cubic foot of solid CH weighs about 31.6 pounds, while 1 cubic foot of liquid CH, weighs only 25.9 pounds. The volume expansion from melting alone is therefore 22.2 percent, giving a linear expansion of over 7.0 percent. Hence, a ship cargo section-measuring 1,000 feet long is, upon the melting of its one-piece, solid CH cargo, subjected to an elongation of up to feet. Even a fraction ofsuch a great, potential elongation is more than enough to split the ship and to cause disasters.

Further, when a large solid (e.g., l0 ft l0 ft X 65 ft on a railroad car or 600 ft X ft X 26 ft in an occean-going vessel) of CH, is subjected to dynamic loads such as occur when the solid CH is impacted in case of railroad derailment or ship collision and grounding. cracks may start and run across the entire length, width or thickness of the solid mass, or even extend into the ship structure. Such crack propagations may be very rapid and violent, causing severe property damages or losses of human lives. This is because many solids including the solid cryogenic media mentioned above are brittle at the cryogenic temperatures (e.g., below 200F), and require very little energy to propagate the cracks once formed.

The CH gas is combustible and, when mixed with the right amount of air, will produce an explosive mixture. It is essential, therefore, that the CH containers be provided with devices to prevent air intrusion thereinto and to dilute the last portion of CH, with inert or noncombustible gases, such as neon, nitrogen, or-CO sufficiently to remove any danger of fire or explosion.

SUMMARY OF THE INVENTION Therefore, to overcome the foregoing problems and disadvantages, the general object of this invention is to provide an economical, integrated, cryogenic storage, transport, and using system having unusual capabilities.

It is another object of the invention to provide an integrated cryogenic system, not only for transport, but also for storage and usage, so that the dangerous CH, fuel is handled in the safe solid-form, yet the cost of repeated freezings and meltings is minimized or completely eliminated.

Another object is to provide means for interrupting crack propagation across a large volume of solid CH cargo, and to provide crack-arresting and energyabsorbing materials in the paths of potential crack formations.

Yet another object is to'divide the solid CH mass into multiple, smaller and more easily vented blocks in individual compartments, each provided with enclosing walls that will absorb a large portion of the crackpropagating energy, and also of the stresses and strains on the container walls due to thermal expansion or melting of the solid CH.,.

Still another object is to provide means for feeding refrigerating fluid in a self-regulated manner according to the local demands in each compartment, so as to avoid severe undercooling and subsequent expansion stresses and strains on the container walls due to later temperature normalization.

Another object is to provide the cryogenic system with devices for preventing air intrusion thereinto.

Yet another object is to provide means for automatically diluting the last portion of CH, remaining in the BRIEF DESCRIPTION OF THE DRAWING For the purpose of illustrating the invention, there is shown in the drawing the forms which are presently preferred, it being understood, however, that the invention is not necessarily limited to the precise arrangements and instrumentarities here shown.

FIG. 1 is a top view of an integrated cryogenic system constructed according to this invention with parts broken away to illustrate the details;

FIG. 2 is a view in section taken as indicated by the line and arrows 22 of FIG. 1;

FIG. 3 is a fragmentary view in perspective of the connecting device between cryogenic compartments;

FIG. 4 shows a cryogenic compartment with expandable enclosing walls;

FIG. 5 shows a cryogenic compartment having a collapsible top and liquid-level sensitive, feeding device;

FIG. 6 shows the construction of a temperaturesensitive, fluid flow control device;

FIG. 7 shows a cryogenic compartment with frozenin supporting rods and an automatic CO diluting device; and

FIG. 8 shows a device to seal off holes in the enclosing walls, or the top of liquid-feeding and gasdischarging conduit, to prevent exposure to the ambient of the cryogenic mediumin the compartment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 'is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

With respect to the specific embodiments of the invention selected for illustration in the drawing, designates generally a gas-tight, hollow-walled and insulated container or tank carried by the cargo section of a truck, railroad car, airplane, water-borne vessel, or other transport vehicle. The container 20 is adapted to contain at atmospheric pressure a mass of a cryogenic medium, i.e., cold boiling cryogenic gaseous medium preferably in the solid state. The material of the hollow container walls 20 is made of (3003, 505 2, 5053, 5456, 6061) aluminum alloys, (5083, 5086, 5356, 5454) Al-Mg alloys, (304, 316) stainless steels, (36% Ni in Fe) Invar, or such plastics as polystyrene, nylon, and Teflon.

An even wider choice of insulation materials and structures in the hollow container walls 20 is possible. These include: corkwood, mineral wood, expanded rubber, volcanic ash, expanded silica, diatomaceous earth, opacified powder (U.S. Pat. No. 2,967,152). Polystyrene or polyurethane foams crack on repeated thermal cycling into the cryogenic temperature range,

but are often good enough, especially when weight and cost are important considerations. Balsa wood has been considered ideal from every viewpoint for many applications (U.S. Pat. No. 2,859,895), including those on occean-going vessels. Special methods for preparing the balsa wood to make the container walls or linings in gas-tight and expansion-proof forms (even without metals or other enclosures) are described in US. Pat. Nos. 2,806,810 and 2,859,895. These insulation materials are in the form of layered structures, generally 6 to 20 inches thick. Another very effective, layered insulation material consists of multiple layers of 2 to 5-mil aluminized Mylar (nylon or polystyrene) sheets separated at to 150 layers per inch by l to 3-micron glass fibers. The space between the hollow walls of the container is filled with insulation materials and is often vacuumed, to reduce gas conduction and to improve insulation (U.S. Pat. No. 2,396,459). The vacuum may even be controllably varied to meet the instantaneous insulation requirements, thereby achieving controlled gasification of the cryogenic medium (U.S. Pat. No. 2,830,444).

As an important feature of the invention, the container is provided therein with a large number of (close-packed) compartments 21 having square, rectangular, or hexagonal shapes of suitable sizes, e.g.,

(from a railroad car measuring 10 ft X 10 ft X 65 ft) over 1,400 blocks 20 in X 20 in X 20 in or smaller for home uses and (from an occean-going vessel measuring 600 ft X ft X 26 ft) over 600 blocks) 10 ft X 10 ft X 20 ft or larger for industrial uses. These sizes to some extent are determined by the venting requirements. Each compartment has its own (six) enclosing walls, although two neighboring compartments not to be separated may share the same wall. The division of the solid cryogenic medium in the container into smaller blocks in the compartments 21 prevents massive or catastrophic cracks because the enclosing walls 22 are designed to absorb much of the impact forces associated with, e.g., ship collisions or groundings; and also because these same walls physically arrest the crack propagation between the blocks. In addition, the walls 22 absorb a significant portion of the stresses and strains due to mismatched thermal expansion and CH, phase change from solid to liquid.

Another feature of the invention is to have the enclosing walls 22 made of polystyrene or polyurethane forms, or of coiled and springy insulating chips 45 compacted or compressed around a rigid metallic or nonmetallic box or structure 46 to form the compartment 21 (FIG. 4). The outside of these walls is covered by a nylon net or bag 47 made of, e.g., l5-mil nylon strings or sheets. These compartments with their enclosing, compressed walls 22 occupy relatively little space during cryogenic transport, liquid filling, storage, or usage. But when separated after filling and freezing therein of the cryogenic liquid, the compressed or compacted insulation materials of the enclosing walls 22 expand and occupy much greater space for enhanced thermal insulation. The nylon (or Mylar) net or bag acts as a reinforcing structure to prevent weakening or disintegration of the insulation materials 45 and also to facilitate handling of these compartments. When such compartments are exposed to the water in the ambient, e.g., to moist air or occean water, insulating ice layers 49 are formed on the outside surfaces to improve insulation and topreve'nt spillage or contamination. The nylon net or bag may be frozen inside the ice layer.

In addition, special externalfilms or nets 48 of airreactive (notched thin aluminum wires or strips), water-dissolving or -disint.egrating (paper) material may, if needed, cover the outside of the enclosing walls 22 and designed (mainly by the material thickness) to be weakened, dissolved, or disintegrated after aspecified time of exposure to the ambient, to allow easy separation and handling of the unexpanded compartments 21 while still yielding the improved and expanded insulation after the specified time.

The nylon or Mylar net 47 is also suitable for anchoring thereto detachable (longitudinal, transverse, vertical, and/or diagonal) tension rods, strings, or straps, so as to tie the neighboring compartments temporarily but strongly together. Other suitable anchoring devices, also useful on the compartments of FIGS. 1, 2 and 4, are holes in, and plugs, hooks, or studs on, the enclosing walls 22.

in one scheme,.the compartments 21 are joined together at room temperature in close-packed and/or stacked forms by 304 or 316 stainless steel 24 inserted in less thermally expansive (lnvar, Mo, W) sleeves 25 that are held or attached to the enclosing walls 22 or integral therewith (FIG. 3). The sleeves and pins extend outwardly from these walls 22 and generally do not extend through the inner enclosing walls unless fluid leveling between compartments is needed. Each pin may be provided with one or more grooves 18 in which to fit rubber O-rings 19 to provide positive liquid or gas sealing.

A vertical (1 to 6-inch aluminum alloy or 304 stain- Ion, and Teflon are 1.21, 1.17, and 1.85 respectively.) Similar values for lnvar and W are 0.045 and.0. 075 re]- spectively. Stainless steel pins 1.997 inches in diameter and fitting snugly into lnvar or W sleeves (2.000 inches ID.) at room temperature, therefore, are easily removed from the sleeves at 280F, because the clerances have now been increased to 7.3 or 6.7 mils, respectively? Nylon, polystyrene, or Teflon pins (3.997 inches diameter) fitting snugly at room temperature into 4.000 inches stainless steel sleeves (or 4.000 inches holes in the compartment walls 22 of stainless steel) will have the clearances increased'at 280F to 39.4, 41.0, or 66.6 mils, respectively. These pins will readily slip out of the sleeves.

The solidified blocks of cryogenic medium in the compartments can be stored, transported, or used as such in their individual, specially insulated compartments 21. Upon arrival at their destinations, they can be easily separated by removing the pins 24 or by disconnecting the fluid conduits, and used either separately, or in groups of 2, 3, 4, neighboring compartments. This scheme saves the cost and time of repeated meltings and freezings.

In case of ship collision or grounding, water may leak through the water permeable container will 20 to reach the compartments 21. The leaked-in water is, however, easily frozen into ice sheets. Detachable rod, string, strap tension members described in connection with FIG. 4 are particularly useful here also, to reinforce the ice layers and to tie together positively the compartments, so as to facilitate handling or recovery. Water may also freeze between the compartments or into the loosened pins 24. To facilitate the removal of less steel) pipe or conduit 27 is generally centrally fixed inside each compartment 21, and extends from the ceiling 28 to the floor 29. This conduit supplies the compartment with the cryogenic medium to be stored, transported, or used. Stacked compartments have their vertical conduits 27 aligned accurately and joined together by common sleeves 30. These sleeves are made of the same less expansive (lnvar, W, Mo) materials and fastened similarly to the ceilings 28 and floors 29. Holes and/or slats 31 are provided on the conduit 27 in all directions and all along its length (but in some cases preferably only near the ceilings 28 to improve heat transfer) for the feeding or filling of the compartments 21, in the form of high-velocity (over 10 in/sec) jet streams.

Another similar, nearby vertical conduit may or may not be needed to feed the refrigerating liquid (e.g., liquid N or lie to freeze CH in the form of sprays or jets, depending on whether the fluid CH and N are mixed together and fed through the same conduit. In FIG. 4, liquid N and CH are shown to flow in two feed pipes or inlet conduits 57 (each provided with a separate regulating valve 58) to form the mixed feed fluids in the feed conduit 27. This spray or jet system,'particularly with mixed fluids, achieves extreme heat transfer efficiency, because of the instant and intimate contact of the refrigerating liquid and cryogenic medium, and also because of the inherent cooling by fluid expansion and countercurrent fluid flow involved.

Notice that from room temperature (about 70F) to a cryogenic temperature of about -280F, the percentage shrinkage for Al, Fe, Ti, Cu, and (304 or 3l6) stainless steel are 0.37, 0.181, 0.134, 0.35, and 0.26 re spectively. Corresponding values for polystyrene, ny-

these various ice layers for the separation of the compartments, special electrical heaters made of (Nichrome) resistance wire or graphite cloth may be laid on the enclosing walls 22. These heaters may even replace the rod, string, or strap types of tension reinforcing members. After these tension members are detached, the compartments may even be blown apart controllably by the gases produced by the electrical heating applied to selected enclosing walls.

The fluid feeding conduit may in some cases be designed to withdraw ahead of the CH liquid-solid interface. The speeds of feeding liquid N and CH and of conduit withdrawal should, however, be accurately controlled, preferably with the aid of automatic liquid level or temperature sensing instruments. A properly positioned, 330-ohm, 0.5-watt carbon resistor with its insulation removed, for example, displays rapidly decreasing resistance with lowering temperature when about 12 volts and 2 ma is applied thereto. The solid columns of CH, left in the ceiling 28 or floor 29 from the conduit holes are easily broken, because of the small hole size and low strength of solid CH when the compartments are separated.

Alternately, the compartment-joining pins 24 or conduit-connecting sleeves 30 may be made of (notched or unnotched rods or pipes of) carbon-steel, Ti, Zn,'or other cryobrittle materials that are easily broken at -280F, to be replaced during the next use cycle. Such sleeves should preferably have, for easy connecting, left-handed threads on the top half but right-handed threads on the lower half (or vice versa), to fit into matching threads on the vertical conduit 27.

The discharge holes, slits, or other openings 31 on the conduit 27 in FIGS. 1, 2, and 5 achieve a unique,

self-regulated fluid flow in response to the fluid level and temperature. This can, be seen as follows. The higher the fluid level above the discharge opening 31, the greater the hydrostatic pressure and, hence, the slower the fluid flow therethrough, as is also the refrigerating demand in this scheme of directional freezing from the bottom up. Further, as the temperature of the fluid CH (and/or N is lowered, its viscosity increases, the flow velocity of the refrigerating liquid N in the Conduit 27 and out gh the fine holes or slots 31 therefore decreases under a constant feed pressure. This condition automatically regulates the feed velocity of the refrigerating material into the compartments 21, according to the local demands. Thus, if one side of, or one level along, the conduit 27 is at a higher fluid temperature than the rest, the refrigerating liquid N feed and, therefore, the jetting and refrigerating actions on this side or at this level are, under a constant feed pressure, greater due to the reduced fluid viscosities with temperature. This gives more local cooling and solidification, and effectively equalizes the temperature among all sides or levels. Where the liquid CH is already frozen, the fluid flow or jetting velocity is zero or practically zero, thereby preventing severe undercooling. Undercooling means subsequent and possibly excessive thermal expansion stresses and strains on the walls of the cargo container due to temperature nor malization.

A fluid-level sensitive, fluid feed control device is shown in FIG. 5. Here, a tubular float 51 is provided with circumferential discharge openings 52 and designed to slide up and down, depending on the fluid level in the compartment, inside and in close-fitting relationship with the conduit 27. Two flexible, plastic tubes 53 and 54 are attached in fluid-tight relationship at their one ends to the ends of the floats 51, and at their other ends to the top and (closed) bottom ends of the conduit 27. Internal fluid pressure forces the plastic sheet tubes to cover and close all the discharge openings except those at a specified level relative to the float 51. The plastic tubes 53 and 54 are long enough and flexible enough to allow the float. 51 to move relatively freely across the height of the compartment.

A one-way control device for positively controlling the local feed velocity is shown in FIG. 6. Here, each feed or discharge opening 31 is made of a suitable bimetallic element 34 (e.g., one thirty-second inch lnvar strip on one thirty-second inch 304 stainless steel strip) attached on its right side to the conduit 27 and a onesixteenth inch to one-eighth inch rubber pad 35 similarly attached on its left side. The free sides of the rubber pad 35 and bimetallic element 34 form a discharge opening 31 of controllable sizes. As the temperature of the fluid next to the fluid control device is lowered, the bimetallic element 34 bends to reduce the fluid flow through the discharge opening, or even to completely stop the flow when the fluid is frozen or nearly so.

A two-way flow control device may be constructed as follows. Select a piece of one-sixteenth inch or oneeighth inch rubber pad or hose, and slit wit a sharp razor blade along its length in various directions to produce the discharge openings similar to those shown as 31 on the conduit 27 of FIGS. 1, 2, 4, and 7. In fact, this rubber hose may form the entire conduit 27. The two sides of each slit match so exactly that ambient moisture readily forms a thin layer of ice along the slit thereby sealing off the CH content from the ambient.

During the supply of the compartment 21, where the fluid temperature is high and viscosity low, more refrigerating liquid N is automatically allowed to pass through these slits. Pressure build-up inside the compartment 21 that exceeds a certain prespecified limit can still blow the grown ice layer off to allow venting. By making the rubber pad or hose thinner and/or more elastic at the cryogenic temperature of freezing CH and by increasin'g the slit length or rubber pad size, the venting pressure can be reduced to any desirable value. On the other hand, by providing for the conduit 27 a thick (over about one-fourth inch) rubber hose with very short and thin slits, the mixed N and CH feed fluids are forced out these slits under great pressures. The adiabatically expanding fluids coming out of the slits will lower the fluid temperature because of the heat adsorption during the expansion. An electrical heater inside the rubber hose may or may not be needed here to gasify the solid so as to clear the hose. The enclosing walls 22 may also be provided with these slitted rubber pads or hoses for venting large blocks or cryogenic solids stored in the compartments 21.

The conduit 27 of FIGS. 1, 2, and 7, possibly made of this specially slitted rubber hose, thus serves not only as the feed conduit for supplying liquid CH and refrigerating liquid N, into the compartments 21, but also as venting-out for the relief of excessive pressures in the compartments during the storage therein of solid (or liquid) CH The same conduit is even useful for supplying gaseous CH, from the gasifying solid CH in the same compartment. After arrival to the designated point, the compartments 21 can be stored and used as a whole, or can be divided into two or more groups. Each group consists of a single compartment or several neighboring compartments with their conduits 27 suitably connected together to supply gaseous Cl-I through the multiple venting valves or slits described above.

As shown in FIGS. 1-3, the enclosing walls 22 of the compartments 21 are hollow and filled therein with such insulation materials as are previously described for the hollow container walls 20. Each of these compartments 21 then forms a self-contained, cryogenic unit suitable for individual storage or usage, even without additional insulation against the ambient.

The enclosing walls 22 may in other cases by very thin and consist of, e.g., only a single, or a few separated layers of aluminized Mylar sheets, so as to have very little mass to cool or ship and to occupy very little space. In this case, the individual compartments containing the cryogenic solid CI-I, must be stored in an insulated container to protect their contents against the ambient heat.

A feature of the invention in some applications is to have these enclosing walls 22 made flexible, such as, e.g., in the form of a simple plastic gas-tight bag. Such walls are incapable of self-supporting or of supporting in a specified shape the cryogenic liquid contained therein. These enclosing walls are, however, rigidized and strengthened by the solid cryogenic medium frozen in situ from the liquid contained therein. Because the walls 22 here are not self-supporting for its fluid contents, they must be externally supported, during the fluid filling operation, by the walls of the container 20 and/or of the neighboring compartments. During usage, the top and side enclosing walls here may even collapse onto the gasifying and receding, solid CH therein (FIG. 5). Such a system prevents vacuum formation in 9 the compartments 21 and allows no air instrusion to contaminate the CH therein or, worse still, to form explosive mixtures with the CH,. The conduit may be collapsible and made, e.g., at least-partly of thin plastic material. Alternately, the top enclosing wall22 may be gas-tightly sealed to the conduit 27 at positions 38 but provided with enough wall material to allow free collapse of the top along a non-collapsible conduit (FIG.

Inside the compartment 21 is also a plastic bag 39 containing Ne, N or CO and designed to brust, upon being warmed up after the CH in the compartment is about all used up, so as to dilute any residual CH in the compartment to harmless proportions and to minimize the danger of explosion (See FIG. 5).

Another feature of the invention, useful in some applications and shown in FIG. 7, is to insert rods 32 in the compartments 21. These rods are fastened together at their uppen ends and/or to the top corners 40 of each compartment 21, so that after the compartment is filled with liquid CH and the liquid frozen in situ, the rods 32 are frozen into the solid CH to form a single or unitary, solid structure for each handling. These rods may be disconnected at their lower ends, or connected together at their lower ends with a chain or ring 33. Such a structure can even be collapsible, when used in conjunction with the collapsible conduit of FIG. 5, or with the withdrawable conduit 27 sliding inside the sleeves 30 of FIGS. 1 and 2. These supporting rods, if made of aluminum, Al-Mg, or other materials more thermally conductive than the solid CH also allow the ambient heat to be conducted therealong into the solid for its controlled gasification. One or more of these rods may even be hollow (i.e., pipes) and provided with the feeding, venting, and/or discharging valves previously described. A rod 32 dropping under its own weight in a collapsible compartment may be so positioned as to break a glass ampoule 36 containing an inerting or diluting gas, such as Ne, N or C0 The conduit 27 of FIGS. 1, 2, 4, 5, and 7; and the through holes of the sleeves 25, 30, and 37 of FIGS. 1, 2, 3, and 7 can be sealed off by means of overlapping, flexible rubber pads, which are similar in construction to the venting valves on the rubber pads or hoses previously described. These pads effectively seal off water vapor from the air, and also the air itself after a layer of ice is formed thereon. A more positive seal comprises a solid plug 41 of CO ice, paraffin, or like material slightly smaller in size than the inner diameter of the conduit or opening. Such a plug is first inserted into the appropriate opening to leave an annular clearance of about 0.010 to 0.200 inch wide. Next, liquid CO is poured into the annular space 42, to be instantly frozen for'completing the seal. Even venting is possible with the plug 41 by, e.g., blowing it off. Further, by decreasing the thickness and/or increasing the diameter of the plug 41, the required venting pressures may be designed into the system. An electrical heater 43 embedded in the solid CO plug allows instant removal of the plug so that more liquid CH and/or N may be fed into the compartment 21, or gasified CH, let out for usage. The plug material may also be different from the material used for finally sealing off the annular space 42. Thus, a paraffin plug 41 may first be used to provide the annular space 42, and this space is later filled with solidifying CO or water.

the system, only a small portion'of the solid CH near the conduit 27 is, at first, thawed or gasified, by heat As another aspect of the invention, during the use of conducted down along the conduit or supplied by a special electrical heater inside the conduit, such as heater 55 of FIG. 5. The bulk of the solid CH particularly portions near the enclosing walls 22, is still at about the melting point of CH, (300F). There is thus very little mismatched expanson between the solid CH and the container walls 20. As more CH is removed by progressive gasification from the inner surface of the central depression (away from the enclosing walls 22), the temperature of the remaining solid CH is still near its melting point. Further, at all times, the liquefying CH always has a free inner surface to expand, so that the expansion stresses and strains due to melting CH, on the container walls 20 are always minimal.

When the fuel gas is being loaded on the transport vehicle and solidified, the refrigerating liquid and even some liquefied fuel invariably escape as mixed evaporated gases. Such mixed gases can be recycled by a con- 1 ventional process which comprises: recovering the mixed, evaporated gases; compressing the recovered mixed gases; expanding and cooling the compressed mixed gases to liquefy the cryogenic medium for resupplying into the compartments; further compressing the remaining gases; and expanding and cooling the remaining gases into the refrigerating fluid to be returned for further use in refrigerating the liquid cryogenic medium in the compartments.

The invention is not to be construed as limited to the particular forms disclosed herein, since these are to be regarded as illustrative rather than restrictive. Skilled persons in the art will have occasions to practice numerous variations on specific features of the invention. It is my desire that all such variations fall within the spirit and scope of the invention as defined by the following claims:

I claim:-

1. A cryogenic system for a single solid cryogenic mewalls allowing any two adjoing compartments to mechanically interact directly therethrough; means for supplying the single cryogenic medium in the fluid state to all the compartments; and means for supplying a refrigerating fluid in heat exchange relationship with the cryogenic medium so as to solidify the fluid cryogenic medium into close-packed but disconnected cryogenic solid blocks of essentially uniform composition in all the compartments thereby preventing the information of a crack extending across the entire length of a dimension of the cryogenic system.

2. The cryogenic system of claim 1 wherein the enclosing walls for each of the compartments are yieldable and require external support for keeping in a specified shape the cryogenic fluid contained therein, but are rigidized and strengthened by the solid cryogenic medium frozen in situ from the fluid contained therein.

3. The cryogenic system of claim 1 wherein the cryogenic medium is harmful when mixed in undiluted form with air from the ambient and including: container containing therein an inerting material for the cryogenic medium; and means for automatically releasing the inerting material from the container when the cryogenic medium in the compartments is about all used up so as to dilute any residual cryogenic medium to harmless proportions.

4. The cryogenic system of claim 3 wherein the inerting material is non-combustible.

5. The cryogenic system of claim 1 including means for pregressively thawing and gasifying in each of the compartments the solid cryogenic medium from the inner surface of a central region away from the side enclosing walls so that the cryogenic medium next to these walls is not appreciably warmed up and the stresses and strains on these enclosing walls due to the thawing and solid-to-liquid phase change of the cryogenic medium is minimal.

6. The cryogenic system of claim 1 including supporting members exposed inside, and at least partly fastened to the walls of, the compartments so that after the compartments are filled with the fluid cryogenic medium and the fluid frozen in situ, the supporting members are frozen into the solid cryogenic medium so as to form a plurality of unitary solid structures therewith.

7. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium comprises at least a retractile fluid supply conduit which retreats: as the fluid level in the compartment heightens.

8. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium comprises at least a supply conduit provided with a plurality of discharge openings alongits length and including: float device floating on the fluid in one compartment; and control means actuated by the float device for covering the discharge openings not intended to be opened.

9. The cryogenic system of claim 8 wherein the control means comprises a tube of flexible sheet material connected to the float device and strong enough to stand the internal pressure of the filling fluid without breaking out of the discharge openings but sufficiently flexible under the buoyancy force of the float device so as to be flexed to uncover successively the discharge openings at higher levels as the fluid level in the compartments heightens.

10. The cryogenic system of claim 1 wherein the compartments are stacked in at least two vertical levels, and the means for supplying the cryogenic medium and refrigerating fluid into a vertical column of compartments are in the form of supply conduits for mixed fluids, the conduit in an upper compartment in the vertical column aligning with, and joining at its lower end with the upper end of, the conduit in its lower adjoining compartment.

11. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium and refrigerating fluid are in the form of a single supply conduit provided with at least one discharge opening through which the cryogenic mixed fluids are discharged into the compartments as at least one high-velocity stream of mixed fluids.

12. The cryogenic system of claim 1 having at least one dimension exceeding 65 feet and wherein the solid cryogenic medium expands substantially on melting and including a substantially gas-tight container to contain the compartments in close-packed manner therein, the layered material having sufficient thickness and deformability relative to the size of the compartments so as to allow for the expansion of the melting solid cryogenic medium without damaging the container walls.

13. The cryogenic system of claim 1 wherein the layered material for the enclosing walls comprises compressed insulation material and including: means for restraining the compressed material of reduced thickness from expansion to its normal thickness; and means responsive to water in the ambient to inactivate the restraining means after a prespecified time of exposure to the ambient, so as to allow the compressed material to be handled within the specified time but to allow it to expand thereafter to its normal thickness thereby enhancing its thermal insulation properties.

14. The cryogenic system of claim 1 whereinthe enclosing walls are collapsible onto the gasifying and receding solid cryogenic medium contained in the compartments so as to prevent vacuum formation therein and air intrusion thereinto.

15. The cryogenic system of claim 10 wherein the supplying means for the cryogenic medium and refrigerating fluid comprises at least one supply conduit, said conduit being also collapsible and movable in coordination with the collapsing enclosing walls of the compartments.

16. The cryogenic system of claim 1 including temperature-sensitive means for connecting the neighboring compartments together and for providing holding strength for handling, said holding strength decreasing with temperature and becoming substantially zero when the compartments are filled with the fluids and the cryogenic medium frozen into solid.

17. The cryogenic system of claim 16 wherein the connecting means comprises a plurality of sleeve-andpin sets, each pin fitting snugly at room temperature inside the sleeve of the same set, the sleeves having a thermal expansion coefficient substantially smaller than that of the pins so that at the temperature of the cryogenic solid medium the pins shrink substantially more than the sleeves for easy disconnections.

18. The cryogenic system of claim 17 including on each of the pins transverse surfaces defining at least one groove; and also including elastic O-ring gas-tightly fitted on the groove to provide positive fluid sealing between the neighboring compartments.

19. The cryogenic system of claim 16 wherein the temperature-sensitive connecting means is made of a cryobrittle material that loses the holding strength at a subatmospheric temperature above the temperature of the cryogenic medium contained in the compartments.

20. The cryogenic system of claim 1 wherein the supplying means for supplying the cryogenic medium comprises a fluid supply conduit which includes: a wall to define a discharge opening thereon; and a flexible member partly attached to the conduit and having its unattached portion in spaced relationship with the opening, the pressure of the fluid supplied to the compartments through the conduit urging the flexible member to part from the opening to allow the cryogenic medium to be fed therethrough into the compartments.

21. The cryogenic system of claim 20 including means responsive to lowering temperature of the fluid in the compartments to reduce at a constant fluid feed pressure the size of the discharge opening.

22. The cryogenic system of claim 20 wherein the flexible member sufficiently opens the discharge opening for venting when the pressure in the compartments exceeds a prespecified value.

23. The method of using a single, liquefiable and solidifiable, gaseous cryogenic medium comprising: providing a plurality of close-packed, adjoining storage compartments with enclosing walls; supplying the cryogenic medium in the liquid state to all the compartments; supplying a refrigerating fluid in heat exchange relationship with the cryogenic medium; and adjusting the two supplying rates so that the liquid cryogenic medium is solidified into close-packed but disconnected cryogenic solid blocks of substantially uniform composition in the compartments.

24. The method of claim wherein each compartment has flexible enclosing walls incapable of supporting in a specified shape the liquid cryogenic medium therein and including: supporting the flexible enclosing walls during the filling of the cryogenic fluids into each compartment to keep it in the specified shape; freezing the cryogenic medium in situ while keeping the support and simultaneously rigidizing and strengthening the enclosing walls for subsequent handling without the aid of the support.

25. The method of claim 23 wherein the enclosing walls are collapsible and including: collapsing the enclosing walls onto the gasifying and receding solid cryogenic medium contained in the compartments to prevent vacuum formation therein and air intrusion thereinto.

26. The method of claim 20 including: providing incompletely connected devices in the compartments; filling the compartments with the liquid cryogenic medium; and freezing in situ the supporting devices into the solid cryogenic medium so as to form therewith a plurality of unitary solid structures having sufficient strengths for handling.

27. The method of claim 23 including: recovering the mixed, evaporated gases; compressing the recovered mixed gases; expanding and cooling the compressed mixed gases to liquefy the cryogenic medium for resupplying into the compartments; further compressing the remaining gases; and expanding and cooling the remaining gases into the refrigerating fluid to be returned for further use in refrigerating the iquid cryogenic medium in the compartments.

28. The method of claim 23 including controllably gasifying the solidified cryogenic medium for distribution and usage in the gaseous form, said controlled gasifying step comprising progressively thawing and gasifying the solid cryogenic medium from the inner surface of a central region away from the side enclosing walls of the compartments, so that the bulk of the solid cryogenic medium in the compartments is not appreciably heated up and the stresses and strains on these enclosing walls due to the thawing and solid-to-liquid phase change of the cryogenic medium is minimal.

29. The method of claim 23 wherein the liquid cryogenic medium in its freezing range has the property of becoming more viscous with reduced temperature, and including: feeding the refrigerating fluid in multiple,

-submerged streams into each compartment under a substantially constant fluid feed pressure; and regulating the local feeding rates of the streams such that when the liquid cryogenic medium in any region of the compartment has a higher temperature relative to those in other regions, the fluid viscosity in this region is reduced and the flow stream velocity of the refrigerating fluid into this region is increased thereby achieving more rapid cooling of this region relative to the other regions.

30. The cryogenic system of claim 1' wherein the enclosing and separating walls are gas-permeable and including electrical heating means to instantly supply sufficient heat to selected compartment walls to gasify the adjacent solid cryogenic medium for blowing apart the adjoining compartments for individual handling thereof.

31. The method of claim 20 wherein the compartment-separating, enclosing walls are gas-permeable and including instantly heating selected locations in the compartment walls to controllably gasify adjacent solid cryogenic medium for blowing apart the adjoining medium can be fed into the compartments to be frozen while subsequently the gasified cryogenic medium can be passed out and including electrical heater in the conduit to heat up and gasify the solid cryogenic medium contained therein.

33. The method of claim 20 wherein the enclosing walls separate the compartmentsand allow any two adjoining compartments to mechanically interact directly therethrough; and wherein the providing step comprises providing in the enclosing walls sufficient crackarresting and energy-absorbing materials to reduce substantially the direct mechanical interaction between the compartments.

34. The method of claim 23 wherein the enclosing walls separate the compartments and allow any two adjoining compartments to mechanically interact directly therethrough; and wherein the providing step comprises providing in the enclosing walls sufficient energy-absorbing materials to absorb significant portions of the stresses and strains on the enclosing walls due to the melting of the solid cryogenic medium in the compartments.

35. The method of claim 23 wherein the gaseous cryogenic medium in undiluted form is combustible in the ambient gases and including automatically diluting the last portion of the gaseous cryogenic medium in the compartments sufficiently to prevent its combustion in the ambient gases.

36. The method of claim 23 including individually venting each of the compartments. l

UNITED STATES PATENT OFFICE CERTIFICATE OF QGRRECTION Patent No. 3,86%,92? Dated Feb., 11, 1975 Inventor(s) Chou H. Li

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column line 31, "blooks)" should read --blooks--. Column 5, line 23, "steel" should read -stee1 pins. Column 5, line +3, "slats" should read --slots--. Column 8, line 21, "blocks or" should read --blooks of--. Column 9, line 11, "brust" should read. --burst--. Claim 1, line 16, "information" should. read ---formation--. Claim 13' line 3, "material" should read --=material of reduced thickness- Claim 13, line delete "of reduced thickness". Claim 15, line 1 4 "10" should read. --1 Claims 2". 26, 31, and 33,5; line 1, "20" should read -23--. Claim 26', line 2, "devices" should read. --supporting dev1c es--- Claim 27, line 8, "iquid" should read --1iquld-=@ Signed and sealed this 24th day of June 1975.

C. MARSHALL DAMN BUTT '3. 2233GT? Commissioner of Eatencs ittevting: Offi car and Trademarl-ts F ORM PO-l050 (10-69) USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE: I969 O366-334 

1. A cryogenic system for a single solid cryogenic medium normally in the gaseous state but capable of being liquefied and solidified at subatmospheric temperatures, comprising: a plurality of adjoining, close-packed compartments adapted to store therein the single cryogenic medium; layered material forming walls separating and enclosing the compartments; the separating walls allowing any two adjoing compartments to mechanically interact directly therethrough; means for supplying the single cryogenic medium in the fluid state to all the compartments; and means for supplying a refrigerating fluid in heat exchange relationship with the cryogenic medium so as to solidify the fluid cryogenic medium into close-packed but disconnected cryogenic solid blocks of essentially uniform composition in all the compartments thereby preventing the information of a crack extending across the entire length of a dimension of the cryogenic system.
 2. The cryogenic system of claim 1 wherein the enclosing walls for each of the compartments are yieldable and require external support for keeping in a specified shape the cryogenic fluid contained therein, but are rigidized and strengthened by the solid cryogenic medium frozen in situ from the fluid contained therein.
 3. The cryogenic system of claim 1 wherein the cryogenic medium is harmful when mixed in undiluted form with air from the ambient and including: container containing therein an inerting material for the cryogenic medium; and means for automatically releasing the inerting material from the container when the cryogenic medium in the compartments is about all used up so as to dilute any residual cryogenic medium to harmless proportions.
 4. The cryogenic system of claim 3 wherein the inerting material is non-combustible.
 5. The cryogenic system of claim 1 including means for pregressively thawing and gasifying in each of the compartments the solid cryogenic medium from the inner surface of a central region away from the side enclosing walls so that the cryogenic medium next to these walls is not appreciably warmed up and the stresses and strains on these enclosing walls due to the thawing and solid-to-liquid phase change of the cryogenic medium is minimal.
 6. The cryogenic system of claim 1 including supporting members exposed inside, and at least partly fastened to the walls of, the compartments so that after the compartments are filled with the fluid cryogenic medium and the fluid frozen in situ, the supporting members are frozen into the solid cryogenic medium so as to form a plurality of unitary solid structures therewith.
 7. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium comprises at least a retractile fluid supply conduit which retreats: as the fluid level in the compartment heightens.
 8. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium comprises at least a supply conduit provided with a plurality of discharge openings along its length and including: float device floating on the fluid in one compartment; and control means actuated by the float device for covering the discharge openings not intended to be opened.
 9. The cryogenic system of claim 8 wherein the control means comprises a tube of flexible sheet material connected to the float device and strong enough to stand the internal pressure of the filling fluid without breaking out of the discharge openings but sufficiently flexible under the buoyancy force of the float device so as to be flexed to uncover successively the discharge openings at higher levels as the fluid level in the compartments heightens.
 10. The cryogenic system of claim 1 wherein the compartments are stacked in at least two vertical levels, and the means for supplying the cryogenic medium and refrigerating fluid into a vertical column of compartments are in The form of supply conduits for mixed fluids, the conduit in an upper compartment in the vertical column aligning with, and joining at its lower end with the upper end of, the conduit in its lower adjoining compartment.
 11. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium and refrigerating fluid are in the form of a single supply conduit provided with at least one discharge opening through which the cryogenic mixed fluids are discharged into the compartments as at least one high-velocity stream of mixed fluids.
 12. The cryogenic system of claim 1 having at least one dimension exceeding 65 feet and wherein the solid cryogenic medium expands substantially on melting and including a substantially gas-tight container to contain the compartments in close-packed manner therein, the layered material having sufficient thickness and deformability relative to the size of the compartments so as to allow for the expansion of the melting solid cryogenic medium without damaging the container walls.
 13. The cryogenic system of claim 1 wherein the layered material for the enclosing walls comprises compressed insulation material and including: means for restraining the compressed material of reduced thickness from expansion to its normal thickness; and means responsive to water in the ambient to inactivate the restraining means after a prespecified time of exposure to the ambient, so as to allow the compressed material to be handled within the specified time but to allow it to expand thereafter to its normal thickness thereby enhancing its thermal insulation properties.
 14. The cryogenic system of claim 1 wherein the enclosing walls are collapsible onto the gasifying and receding solid cryogenic medium contained in the compartments so as to prevent vacuum formation therein and air intrusion thereinto.
 15. The cryogenic system of claim 10 wherein the supplying means for the cryogenic medium and refrigerating fluid comprises at least one supply conduit, said conduit being also collapsible and movable in coordination with the collapsing enclosing walls of the compartments.
 16. The cryogenic system of claim 1 including temperature-sensitive means for connecting the neighboring compartments together and for providing holding strength for handling, said holding strength decreasing with temperature and becoming substantially zero when the compartments are filled with the fluids and the cryogenic medium frozen into solid.
 17. The cryogenic system of claim 16 wherein the connecting means comprises a plurality of sleeve-and-pin sets, each pin fitting snugly at room temperature inside the sleeve of the same set, the sleeves having a thermal expansion coefficient substantially smaller than that of the pins so that at the temperature of the cryogenic solid medium the pins shrink substantially more than the sleeves for easy disconnections.
 18. The cryogenic system of claim 17 including on each of the pins transverse surfaces defining at least one groove; and also including elastic O-ring gas-tightly fitted on the groove to provide positive fluid sealing between the neighboring compartments.
 19. The cryogenic system of claim 16 wherein the temperature-sensitive connecting means is made of a cryobrittle material that loses the holding strength at a subatmospheric temperature above the temperature of the cryogenic medium contained in the compartments.
 20. The cryogenic system of claim 1 wherein the supplying means for supplying the cryogenic medium comprises a fluid supply conduit which includes: a wall to define a discharge opening thereon; and a flexible member partly attached to the conduit and having its unattached portion in spaced relationship with the opening, the pressure of the fluid supplied to the compartments through the conduit urging the flexible member to part from the opening to allow the cryogenic medium to be fed therethrough into the compartments.
 21. The cryogenic system of claim 20 including means responsive to Lowering temperature of the fluid in the compartments to reduce at a constant fluid feed pressure the size of the discharge opening.
 22. The cryogenic system of claim 20 wherein the flexible member sufficiently opens the discharge opening for venting when the pressure in the compartments exceeds a prespecified value.
 23. The method of using a single, liquefiable and solidifiable, gaseous cryogenic medium comprising: providing a plurality of close-packed, adjoining storage compartments with enclosing walls; supplying the cryogenic medium in the liquid state to all the compartments; supplying a refrigerating fluid in heat exchange relationship with the cryogenic medium; and adjusting the two supplying rates so that the liquid cryogenic medium is solidified into close-packed but disconnected cryogenic solid blocks of substantially uniform composition in the compartments.
 24. The method of claim 20 wherein each compartment has flexible enclosing walls incapable of supporting in a specified shape the liquid cryogenic medium therein and including: supporting the flexible enclosing walls during the filling of the cryogenic fluids into each compartment to keep it in the specified shape; freezing the cryogenic medium in situ while keeping the support and simultaneously rigidizing and strengthening the enclosing walls for subsequent handling without the aid of the support.
 25. The method of claim 23 wherein the enclosing walls are collapsible and including: collapsing the enclosing walls onto the gasifying and receding solid cryogenic medium contained in the compartments to prevent vacuum formation therein and air intrusion thereinto.
 26. The method of claim 20 including: providing incompletely connected devices in the compartments; filling the compartments with the liquid cryogenic medium; and freezing in situ the supporting devices into the solid cryogenic medium so as to form therewith a plurality of unitary solid structures having sufficient strengths for handling.
 27. The method of claim 23 including: recovering the mixed, evaporated gases; compressing the recovered mixed gases; expanding and cooling the compressed mixed gases to liquefy the cryogenic medium for resupplying into the compartments; further compressing the remaining gases; and expanding and cooling the remaining gases into the refrigerating fluid to be returned for further use in refrigerating the iquid cryogenic medium in the compartments.
 28. The method of claim 23 including controllably gasifying the solidified cryogenic medium for distribution and usage in the gaseous form, said controlled gasifying step comprising progressively thawing and gasifying the solid cryogenic medium from the inner surface of a central region away from the side enclosing walls of the compartments, so that the bulk of the solid cryogenic medium in the compartments is not appreciably heated up and the stresses and strains on these enclosing walls due to the thawing and solid-to-liquid phase change of the cryogenic medium is minimal.
 29. The method of claim 23 wherein the liquid cryogenic medium in its freezing range has the property of becoming more viscous with reduced temperature, and including: feeding the refrigerating fluid in multiple, submerged streams into each compartment under a substantially constant fluid feed pressure; and regulating the local feeding rates of the streams such that when the liquid cryogenic medium in any region of the compartment has a higher temperature relative to those in other regions, the fluid viscosity in this region is reduced and the flow stream velocity of the refrigerating fluid into this region is increased thereby achieving more rapid cooling of this region relative to the other regions.
 30. The cryogenic system of claim 1 wherein the enclosing and separating walls are gas-permeable and including electrical heating means to instantly supply sufficient heat to selected compartment walls to gasify the adjacent solid cryogenic medium for blowing apart the adjoining compartments for individual handling thereof.
 31. The method of claim 20 wherein the compartment-separating, enclosing walls are gas-permeable and including instantly heating selected locations in the compartment walls to controllably gasify adjacent solid cryogenic medium for blowing apart the adjoining compartments for individual handling thereof.
 32. The cryogenic system of claim 1 wherein the supplying means for the cryogenic medium is in the form of a supply conduit provided with at least one two-way discharge opening through which the fluid cryogenic medium can be fed into the compartments to be frozen while subsequently the gasified cryogenic medium can be passed out and including electrical heater in the conduit to heat up and gasify the solid cryogenic medium contained therein.
 33. The method of claim 20 wherein the enclosing walls separate the compartments and allow any two adjoining compartments to mechanically interact directly therethrough; and wherein the providing step comprises providing in the enclosing walls sufficient crack-arresting and energy-absorbing materials to reduce substantially the direct mechanical interaction between the compartments.
 34. The method of claim 23 wherein the enclosing walls separate the compartments and allow any two adjoining compartments to mechanically interact directly therethrough; and wherein the providing step comprises providing in the enclosing walls sufficient energy-absorbing materials to absorb significant portions of the stresses and strains on the enclosing walls due to the melting of the solid cryogenic medium in the compartments.
 35. The method of claim 23 wherein the gaseous cryogenic medium in undiluted form is combustible in the ambient gases and including automatically diluting the last portion of the gaseous cryogenic medium in the compartments sufficiently to prevent its combustion in the ambient gases.
 36. The method of claim 23 including individually venting each of the compartments. 